Maria Sharapova returns a shot to Camila Giorgi during Monday’s third-round match at the BNP Paribas Open in Indian Wells, Calif.

INDIAN WELLS, Calif. — Camila Giorgi upset defending champion Maria Sharapova 6-3, 4-6, 7-5 in the third round of the BNP Paribas Open on Monday, giving the young Italian her first victory over a top-five player.

Sharapova’s lob sailed long on Giorgi’s first match point, one of 58 errors for the Russian in her first loss to a player ranked outside the top 30 since Wimbledon last year.

“She’s someone that doesn’t give you much rhythm,” Sharapova said. “She’s quite aggressive, but some shots she hits incredible for a long period of time. Sometimes they go off a bit. If I’m speaking about my level, it was nowhere near where it should have been.”

Ranked 79th in the world, Giorgi made it through qualifying to play Indian Wells for the first time. She improved to 3-2 against top-10 opponents. The 22-year-old led 4-2 in the final set, but Sharapova broke Giorgi twice to tie it at 5.

“I was trying to just play my game, and maybe I accelerate more than the other set,” Giorgi said. “I just play more aggressive.”

Giorgi then broke Sharapova at love before serving out the match, overcoming her 11th double fault to set up match point. Giorgi had 48 unforced errors and 24 winners.

“If she can play like that on a consistent basis, she will be a good player,” Sharapova said.

American Sloane Stephens was to play Ana Ivanovic, and Tommy Haas took on Kei Nishikori of Japan in night matches.

Sharapova had ample opportunities to win the match. Tied 4-all in the third, she was broken when her forehand was called long and Sharapova raised her arms. The chair umpire took the gesture to mean Sharapova was challenging the call, and the call showed the ball was out.

Sharapova argued she was only throwing her arms up as if to ask, “Who made the call?” But the umpire disagreed, and Sharapova retreated to her sideline chair trailing 5-4.

She said she heard the out call come from someone in Giorgi’s box rather than the line judge first.

“I’m sure it’s the heat of the moment, but I don’t think he had any right to call out the ball before the line judge did,” said Sharapova, who didn’t disagree that the ball was out.

Murray had his hands full playing for the first time against Vesely, who at age 20 is the youngest member of the top 100 of the ATP Tour rankings and was competing in his first Masters 1000 event.

Murray had 47 of the 99 unforced errors during the nearly three-hour match in the 80-plus-degree heat of the Southern California desert. The third set featured six service breaks, with Murray taking the last two.

“It was that sort of match where at no stage did either of us play well at the same time,” Murray said. “There wasn’t one period where I thought the level of tennis from both of us was high at the same time. That can create a lot of breaks and a lot of sort of back and forth swings in the match.”

Vesely staved off two match points with a pair of winners. But the Czech double-faulted to set up Murray’s third match point and he netted a forehand volley to end his upset bid.

Federer has regained some of the momentum that eluded him last year, when he won just one title. Last week, he won the tournament in Dubai with victories against Novak Djokovic and Tomas Berdych. At the Australian Open, the former world No. 1 earned wins over Jo-Wilfried Tsonga and Murray before losing to Rafael Nadal.

“I feel different this year,” Federer said. “Now I feel like I’m in a good place. Zen on the court. Even if I won 6 and 6 today, I just feel like I was calm. Those are the moments where you feel there is confidence around somewhere.”

Li closed out the match with an ace, one of her 15 winners in a match in which the Chinese star had 28 unforced errors. The Australian Open champion has never been past the semifinals in six previous appearances at Indian Wells.

Li is playing as the No. 1 seed in a major tournament for the first time.

“It is different,” she said. “Now is high attention; everyone is focused. It’s very tough to hang in there, especially at the beginning of the tournament.”

Trailing 4-3 in the second set, Li rallied to win the final three games and dispatch Pliskova.

Aleksandra Wozniak of Canada defeated 21st-seeded Anastasia Pavlyuchenkova of Russia 6-1, 6-7 (3), 6-0 to set up a fourth-round match against Li.